Both hyperpolarized xenon and helium have demonstrated utility in lung imaging and quantifying lung disease. In contrast to helium, however, hyperpolarized xenon has a high solubility in fluids and tissues and a characteristic chemical shift, revealing its microscopic environment in dissolved-phase imaging. An imaging protocol to investigate dissolved-phase imaging in humans could beneficially utilize several breath holds of roughly one liter each of highly polarized gas. [unreadable] [unreadable] The UNH group has developed a new type of xenon polarizer that flows the gas mixture at relatively high velocity and low pressure along a direction opposite to the laser beam, producing polarization of over 50% for small quantities and 20% for a production rate of over four liters per hour. The figure-of-merit (polarization times production rate) of this polarizer presently exceeds all other polarizer technologies by an order of magnitude. [unreadable] [unreadable] The 500 torr operating pressure represents a compromise between higher laser absorption (at higer pressure) and faster spin-exchange rates (at lower pressure). Our numerical simulations indicate that output magnetization scales with absorbed laser power, that is, power within a narrow range around the spectral absorption band. Our research group recently commissioned a 115W laser with narrowed O.Snm spectral linewidth, the world's brightest laser at 794.7nm. [unreadable] [unreadable] We request STTR funding to further develop and commercialize high-power spectrally narrowed lasers for spin-exchange optical pumping of hyperpolarized gas. For Phase I we intend to scale up this spectrally narrowed laser technology to over 400W, install it on a suitably adapted xenon polarizer, and confirm that magnetization output is increased at least 4-fold. For Phase II we will increase efficiency and decrease size by theoretical and experimental optimization of the cavity; characterize the performance of individual components and the full laser; develop supply channels with vendors; engineer mechanical stability and adjustability; determine operational limits; and document safety. We can then commercially offer narrowed lasers from 100W to perhaps as high as 800W for spin-exchange polarization of both helium and xenon. [unreadable] [unreadable] [unreadable]